There are known three tracking methods. In the first method, a terminal of a moving object reports an own location to a tracking server (hereinafter, referred to as “tracking platform” or “platform”) at constant time intervals. In the second method, the platform requests the terminal to send the location of the moving object. In the third method, when road network data is available, the terminal reports the location of the moving object to the platform based on road segment information only if road segments are changed.
In the first method, the terminal reports its location to the platform every second or every minute and the platform processes data on the reported location. Accordingly, an excessive overloading of communication data load between the terminal and the platform can be caused. Therefore, the first method is not suitable for urgent cases with the need for urgency and accuracy.
In the second method, when the time interval at which the platform acquires the location of the terminal decreases, the platform requests the location of the terminal more frequently, and the terminal has to collect, calculate, and report the location information in response to the request. Accordingly, the excessive overloading of communication data load between the terminal and the platform may be caused as the first method. In addition, the platform needs to track the location of the terminal in real time, which is not supported by the second method.
In the third method, the terminal has to report the location of the terminal to the platform every road segment. In this method, the frequency of reporting the location is less than that of the first or second method and the platform can track the terminal in real time. However, if the road network is consisted of a number of small road segments, the communication load between the terminal and the platform may be increased as the first and second methods. The reason is, as the number of road segments increases, the number of issuing updates also increases.